Active Disturbance-Rejection Controller (ADRC)-Based Torque Control for a Pneumatic Rotary Actuator with Positional Interference

The compressibility of air, the uncertainty of dynamic models, and the existence of friction make pneumatic servo systems exhibit strong nonlinearity. Furthermore, the confluence of pneumatic-system nonlinearity and interference from the position system induces oscillations within the system, thereby posing a formidable challenge for achieving precise torque control. This study ensures precise torque control in a pneumatic actuator amid interference from the position system and proposes a novel active disturbance-rejection controller integrated with a Kalman filter. Firstly, in response to the oscillation stemming from the inherent nonlinearity of the pneumatic system and interference from the position system, this paper designs an active disturbance-rejection controller (ADRC) with robust anti-interference capabilities aimed at mitigating system oscillations. Secondly, to address the issue of sensor noise interfering with the ADRC and causing system oscillation, a first-order Kalman filter is designed to provide real-time and more accurate state estimation, effectively reducing oscillations and improving the robustness of the system. Finally, using the Lyapunov stability theory, the effectiveness of both the nonlinear extended observer and the convergence of the nonlinear error-state controller in the ADRC is proven. Experimental results indicate that the proposed controller reduces system oscillations and improves control accuracy.